arXiv subjects

Adam Rycerz

Publications and source records attributed to Adam Rycerz.

44 records · Page 3Linked to original sources

arXiv2006

Entanglement and transport through correlated quantum dot

We study quantum entanglement in a single-level quantum dot in the linear-response regime. The results show, that the maximal quantum value of the conductance 2e^2/h not always match the maximal entanglement. The pairwise entanglement between the quantum dot and the nearest atom of the lead is also analyzed by utilizing the Wootters formula for charge and spin degrees of freedom separately. The coexistence of zero concurrence and the maximal conductance is observed for low values of the dot-lead hybridization. Moreover, the pairwise concurrence vanish simultaneously for charge and spin degrees of freedom, when the Kondo resonance is present in the system. The values of a Kondo temperature, corresponding to the zero-concurrence boundary, are also provided.

cond-mat.str-el↗

arXiv2006

Electronic structure and parity effects in correlated nanosystems

We discuss the spectral, transport and magnetic properties of quantum nanowires composed of N\leq 13 atoms and containing either even or odd numbers of valence electrons. In our approach we combine Exact Diagonalization and Ab Initio calculations (EDABI method). The analysis is performed as a function of the interatomic distance. The momentum distribution differs drastically for those obtained for even N with those for odd N, whereas the Drude weight evolves smoothly. A role of boundary conditions is stressed.

cond-mat.str-el↗

arXiv2006

Microwave absorption by the Josephson-junction network in a low field: A realistic model for ceramic high-temperature superconductor

We discuss the applied magnetic field dependence of the absorption of microwaves by a 3-dimensional array up to 30x30x30 Josephson junctions with random parameters including the resistivity, capacity and inductance of each junction. The numerical simulation results for the networks show characteristic microwave absorption anomalies observed in the ceramic samples of high temperature superconductor YBa2Cu3O(7-x). We also provide a discussion of the absorption in simple analytical terms of Josephson loop instabilities.

cond-mat.supr-con↗

arXiv2006

Conductance of a double quantum dot with correlation-induced wave function renormalization

The zero-temperature conductance of diatomic molecule, modelled as a correlated double quantum dot attached to noninteracting leads is investigated. We utilize the Rejec-Ramsak formulas, relating the linear-response conductance to the ground-state energy dependence on magnetic flux within the framework of EDABI method, which combines exact diagonalization with ab initio calculations. The single-particle basis renormalization leads to a strong particle-hole asymmetry, of the conductance spectrum, absent in a standard parametrized model study. We also show, that the coupling to leads V=0.5t (t is the hopping integral) may provide the possibility for interatomic distance manipulation due to the molecule instability.

cond-mat.str-el↗

arXiv2004

Fundamental properties, localization threshold, and the Tomonaga--Luttinger behavior of electrons in nanochains

We provide a fairly complete discussion of electronic properties of nanochains modelling the simplest quantum nanowires, within the recently proposed approach combining Exact Diagonalization in the Fock space with an Ab Initio calculations (EDABI method). In particular, the microscopic parameters of the second-quantized Hamiltonian are determined and the evolution of the system properties is traced in a systematic manner as a function of the interatomic distance (the lattice parameter, R). Both the many-particle ground state and the dynamical correlation functions are discussed within a single scheme. The principal physical results are: (i) the evolution of the electron momentum distribution and its analysis in terms of the Tomonaga-Luttinger scaling, (ii) the appearance of mixed metallic and insulating features partial localization) for the half-filled band case, (iii) the appearence of a universal renormalized dispersion relation of electron energy, which incorporates both the band-structure and the Hubbard-splitting features in the presence of electron interactions, and (iv) the transformation from a highly-conducting nanometalic state to the charge-ordered nanoinsulator in the quarter-filled case. The analysis is performed using an adjustable Gaussian 1s-like basis set composing the Wannier functions, as well as includes the long-range Coulomb interaction.

cond-mat.str-el↗

arXiv2002

Collective Properties of the Exactly Solvable Model of Ion-Channel Assemblies in a Biological Cell Membrane

The behaviour of a system of ion channels formed across the cell membrane is presented. The infinite number of channels with an infinite coupling is introduced first as a reference point for the detailed derivation of the thermal-equilibrium probability distribution and the classification of the phase transitions. Fluctuations in a finite system are discussed next. We propose a new, step-like model of the ion channel switching, for which we provide the analytical results. The relation of this model to experiment is also provided. Finally, the master equation for the finite channel-number membrane is analysed numerically with the help of an exact-diagonalization technique. In particular, the decay-time of a metastable solution is estimated. The results do not agree with those obtained perturbationally, the difference is explained by the proposed frozen-diffusion approach.

physics.bio-ph↗

arXiv2001

Electron localization in one dimension obtained from combined exact diagonalization - ab initio approach

Exact ground-state properties are presented by combining the diagonalization in the Fock space (and taking all hopping integrals and all two-site interactions) with the ab initio optimization of the Wannier functions. Electrons are essentially localized for the interatomic distance R~2A for s-like states, when the quasiparticle mass is divergent. The momentum distribution dispersion is proposed to define the localization order parameter. Dimerization and zero-point energies are also discussed. The method provides convergent results for N>=8 atoms.

cond-mat.str-el↗

arXiv2001

Electronic states, Mott localization, electron-lattice coupling, and dimerization for correlated one-dimensional systems. II

We discuss physical properties of strongly correlated electron states for a linear chain obtained with the help of the recently proposed new method combining the exact diagonalization in the Fock space with an ab initio readjustment of the single-particle orbitals in the correlated state. The method extends the current discussion of the correlated states since the properties are obtained with varying lattice spacing. The finite system of N atoms evolves with the increasing interatomic distance from a Fermi-liquid-like state into the Mott insulator. The criteria of the localization are discussed in detail since the results are already convergent for N>=8. During this process the Fermi-Dirac distribution gets smeared out, the effective band mass increases by ~50%, and the spin-spin correlation functions reduce to those for the Heisenberg antiferromagnet. Values of the microscopic parameters such as the hopping and the kinetic-exchange integrals, as well as the magnitude of both intra- and inter-atomic Coulomb and exchange interactions are calculated. We also determine the values of various local electron-lattice couplings and show that they are comparable to the kinetic exchange contribution in the strong-correlation limit. The magnitudes of the dimerization and the zero-point motion are also discussed. Our results provide a canonical example of a tractable strongly correlated system with a precise, first-principle description as a function of interatomic distance of a model system involving all hopping integrals, all pair-site interactions, and the exact one-band Wannier functions.

cond-mat.str-el↗